These investigations are designed to substantiate and extend in vitro neurochemical observations to the integrated waking primate and provide a primate system in which it is possible to devise investigative strategies or paradigms for investigations of neurochemical and neuropharmacological aspects of normal and disordered central nervous system function in man. Particular emphasis has initially been placed on studies of the circadian fluctuations of central monoamines and the test of newly devised labelling procedures, using non-radioactive isotopes, for clinical investigations of neurotransmitter metabolism.